The conventional high-tenacity heat-resistant fibers such as para-polymerized aromatic polyamide fibers can only give a spun yarn with extremely low tenacity, and the original tenacity of these fibers is not fully utilized for the purpose of making a spun yarn with high tenacity and high heat resistance. As an attempt to make good use of fiber tenacity, there has been proposed a spun yarn having a single yarn fineness of 1 denier or less, preferably 0.8 denier or less, and also having a small number of fluffs, which is called "special spun yarn" (see, e.g., JP-A 4-361633/1992).